1. Field of the Invention
The present invention relates generally to hydrodynamic fluid bearings for motors such as are utilized in hard disk drives, and more particularly to methods for determining whether sufficient oil resides within the bearing following assembly thereof.
2. Description of the Prior Art
Hydrodynamic fluid bearing motors are utilized in applications that require high speed reliable performance, such as in hard disk drives. Such motors have close tolerances and require the insertion of an adequate quantity of fluid into the hydrodynamic fluid bearing during manufacturing. If insufficient fluid is inserted into the bearing during the manufacturing process, the operational lifetime of the motor can be shortened significantly. However, because such motors are sealed following the fluid insertion step, there has been no way to determine, following sealing of the motor, whether sufficient oil was inserted therewithin. Therefore, while an important step in the quality control evaluation of such motors should involve a determination of whether sufficient fluid has been inserted into the hydrodynamic fluid bearing during the manufacturing thereof, there has been no method to make this determination.
The present invention provides a solution to this problem in a recognition that the fly-height of the hydrodynamic fluid bearing is affected by the quantity of fluid within the bearing, and in the development of a device and method for determining the fly-height of the hydrodynamic fluid bearing. As a result, the present invention provides a device and method for determining the fly-height of the bearing as a measure of the sufficiency of oil therewithin, and thus a measure of the quality of the motor.